This invention relates to an improved return trainer for recentering conveyor belts moving in a direction of travel.
Conveyor belts are used to convey a variety of materials such as ore, some of which are quite heavy and difficult to load evenly on a belt. When the material on the belt is not centered on the belt, the uneven loading causes the belt to shift laterally to one side or the other of supporting rollers necessitating frequent adjustments and more or less constant attention by the operators.
There are other factors making it difficult to maintain an alignment of the conveyor belt on the supporting rollers such as the stretching or warping of the belt due to temperature changes or wetting or the build up or uneven wear of the supporting rollers. In a typical installation, a conveyor system for handling ore may be one-half mile long and will have the endless belt approximately one mile long. The cost of these belts alone are very expensive. Should the belt be laterally displaced while it is running and come into contact with the support member, it will rapidly be worn and if not repaired the belt will deteriorate. It is very expensive to repair such belts because of the size and weight of the belt and it is imperative that belt wear be minimized.
To correct the problem, a number of devices have been used to sense the lateral drift of the conveyor belt so as to actuate some mechanism which will recenter the conveyor belt along its normal travel path. For example U. S. Pat. No. 2,751,067 to Nicholson shows a pair of idler wheels which are mounted on axles at the edge of the travelling belt which axles are oriented in a direction perpendicular to the direction of belt travel. If the traveling belt moves laterally, the idler wheels move the belt to a centered position on the support roller.
Another type of training device is shown in U.S. Pat. No. 3,303,924 to Hartzell Jr. With this arrangement, two (2) idler wheels are mounted on axles which are at an angle to the axle of the support roller but are in approximately the same vertical plane. Guide rollers are mounted at the edges of the idler rollers and when the belt touches the guide rollers, the idler roller swivels on the support member urging the belt back to its normal position.
Another type of device is shown in U.S. Pat. No. 3,913,729 to Andrews which shows a pair of idler rollers mounted at the opposite edges of the travelling belt. As the belt edge engages one of the rollers, the support roller is pivoted to urge the belt back to its normal position.
Other devices have used a pivotal framework to recenter the conveyor belt. The pivotal framework pivots about a vertical axis with the framework extending downstream in the direction of the conveyor belt travel. These devices have rollers for engaging the edges of the conveyor belt at locations that are downstream from the pivotal axis of the framework. As the framework pivots about the pivotal axis, the streaming motion of the conveyor belt across the pivoted support roller recenters the conveyor belt. An example of this type of device is shown in U.S. Pat. No. 4,506,782 to Jenneret et al.
All of these approaches to the problem of aligning a travelling conveyor belt utilize friction between the belt and the trainer to move the belt in the desired direction. All of these approaches will not do the job when there is little friction between the belt and the trainer due to moisture, ice or snow. Under these circumstances, the belt may merely flip up over the guide rollers located at the edge of the travelling conveyor belt causing the devices to not operate in a normal manner.
From the above it can be seen that an improved belt training device is needed which can keep the belt centered along the center line in the direction of travel and prevent the belt from jumping off the training device whenever ice, moisture or other debris gets caught near the guide rollers.